The invention concerns a floor table of a concrete formwork for producing a concrete floor, comprising at least one front and one rear holder for mounting at least one front and at least one rear ligament of a crane harness.
Floor tables of this type are disclosed in U.S. Pat. No. 3,787,020. The displacement of such floor tables is disclosed in the company document “Flying Procedure” of FORM-EZE Systems Inc.
Concrete formworks are used to build concrete buildings. The formwork thereby defines a space for liquid concrete and can be removed when the concrete has hardened.
So-called floor tables are conventionally used to produce concrete floors. Floor tables have a relatively large, flat formwork surface, e.g. of a format of 6×24 m. Assembly and disassembly of a floor formwork using floor tables requires only a few, but complex assembly steps, and, in particular, a crane for displacing the floor tables.
The conventional construction of a storey of a building using floor tables is described below.
A floor table comprising i.a. an upwardly facing formwork surface is positioned onto a floor surface. The floor table is initially roughly positioned, generally by means of a crane. Further horizontal positioning is realized by roller means, such as assembly trolleys, articulated rollers, rigid rollers, tank rollers etc. The upper edge of the formwork surface is then disposed at a distance from the upper edge of the floor in correspondence with the room height to be produced, wherein spindles or hydraulically actuated lifting means are conventionally used to vertically adjust the floor table. Further floor tables and/or vertically oriented formwork elements are disposed at the edges of the floor table and corresponding reinforcing materials are disposed on the floor tables. Liquid concrete is subsequently poured into and distributed on the formwork surface of the floor table and is left until the concrete, i.e. the concrete floor to be produced, has hardened.
After hardening, the formwork is at first removed from the floor table and the floor table is lowered relative to the hardened concrete floor, e.g. by using the above-mentioned spindles. The stroke of the lowering motion should be minimum to save assembly time. The floor table is disposed on roller means. The floor table without formwork is then manually displaced in a horizontal direction by technicians, such that the floor table projects beyond the hardened concrete floor. Holders for the ligaments of a crane harness are provided on the upper side of the floor table on both sides of the center of gravity. As soon as the floor table has been pushed out to a sufficient degree, such that at least a first part of these holders projects outward from below the hardened concrete floor, a technician climbs onto the upper side of the floor table and fastens the ligaments of a crane harness to the exposed holders, optionally with the technician standing on the formwork surface and opening flaps therein. If necessary, the floor table is pushed further out until the remaining holders also project from below the hardened concrete floor, and a technician, standing on the formwork surface, fastens the other ligaments to the holders.
According to FORM-EZE Systems Inc., the floor table is extracted directly from underneath the hardened concrete floor to such an extent that all holders on the upper side of the floor table are exposed to allow the technician to fasten all ligaments of the crane harness. Usually, the floor table is as wide as the hardened concrete floor and the center of gravity of the floor table must be displaced beyond the edge of the floor. As a result, the floor table tilts and its inner, upper edge must be supported on the lower side of the hardened concrete floor.
When the crane harness has been completely fastened, the ligaments can be tightened and further conventional handling of the floor table using a crane is possible. The floor table is then completely extracted or pivoted out of the region between the floor and the hardened floor and is lifted and disposed on the hardened floor. The hardened floor may then serve as floor for adding on a further storey.
When displacing a floor table as recommended by FORM-EZE Systems Inc., the crane harness can be mounted directly above the center of gravity of the floor table immediately after assembly.
One disadvantage of this prior art is that the technician may have to walk on an inclined formwork surface of a floor table in order to fasten the ligaments. The section of the floor table on which the technician moves, projects past the hardened concrete floor and typically also beyond the floor, such that the worker must be specially secured for this work. The surface of the floor table may be moist and slippery after removal of the formwork, in particular, due to formwork oil and condensed water. Another disadvantage is the fact that it requires considerable effort to horizontally displace the floor table, i.e. the manual labor of several technicians.
In contrast thereto, it is the object of the present invention to provide a floor table which can be moved out from beneath a floor and displaced with less expense and increased safety for the technicians.